Reliance on Cookies without Validation and Integrity Checking

Description

Attackers can easily modify cookies, within the browser or by implementing the client-side code outside of the browser. Reliance on cookies without detailed validation and integrity checking can allow attackers to bypass authentication, conduct injection attacks such as SQL injection and cross-site scripting, or otherwise modify inputs in unexpected ways.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code excerpt reads a value from a browser cookie to determine the role of the user.

Cookie[] cookies = request.getCookies();
for (int i =0; i< cookies.length; i++) {
  Cookie c = cookies[i];
  if (c.getName().equals("role")) {
    userRole = c.getValue();
  }
}

It is easy for an attacker to modify the "role" value found in the locally stored cookie, allowing privilege escalation.

See Also